GAZA, Jan 12 (Reuters) - For weeks, Gazans have been making do with less than half their usual electricity supply - barely a few hours a day - with no sign of the shortages alleviating anytime soon, fuelling distress and frustration among the population.

Normally, Gaza's power alternates on eight-hour cycles, with generators providing electricity to those that can afford it in the down times. But since late last year, there have been only three or four hours of electricity a day in total.

The costs of running generators have spiralled. People are trying to light and heat their homes with candles or by burning scrap wood. Families wake in the middle of the night, when the power sometimes comes on, to take showers or wash clothes.

"We live like rats," said Mazen Abu Reyala, an unemployed fisherman and father of five, sitting around a primitive stove that he uses to warm his house. "Should I wait until we get burned? Or should I wait to return home and see that my children burned themselves because they lit candles."

The cause of the shortage is on the one hand simple and on the other complicated, with some citizens blaming Hamas, the Islamist group that runs Gaza, Hamas officials blaming the rival Palestinian Authority, based in the Israeli-occupied West Bank, and still others pointing the finger at Israel.

The simple explanation is that Gaza requires 450-500 MegaWatts of power a day but is receiving barely a third of that. About 30 MW produced by its own ageing power plant, 30 MW imported from Egypt and 120 MW supplied from Israel.

With temperatures dropping to four or five degrees centrigrade at night, people are trying to run electric heaters and radiators, driving up power demand.

The local power plant, which was heavily damaged by Israeli bombing during a war in 2006 and remains only at about half of potential capacity, could produce slightly more, but there are not enough funds to buy fuel to boost output.

With unpaid consumer bills of around $1 billion, the power company is not in a position to seek more credit. Officials say they need $500 million to rehabilitate the power network. But with Israel and Egypt maintaining a tight blockade on Gaza, getting replacement parts is not even that straight forward.

The Palestinian Authority, which pays for power supplied by Israel and Egypt, normally transfers fuel to Gaza and exempts it from most taxes. But because of its own financial constraints, it is no longer offsetting all the tax, angering Hamas.

Spokesman Fawzi Barhoum said Hamas was open to solutions and accused the Palestinian Authority of using the crisis as a mean to "damage Hamas's image and sanction Gaza's people".

Israel's electricity company could supply more power, and has provisions in place to do so, but it has not been paid for all the electricity it has supplied in the past and wants financial guarantees before it delivers more.

Gaza's population of two million is growing increasingly angry. There have been protests and more are planned. Adel Al-Mashwakhy, a local comedian, was detained on Wednesday, hours after posting a video on Facebook criticising Hamas for the shortages. The video was soon watched 180,000 times.

"There is no work, no crossings, no food, no water to drink and also there is no electricity," he says in the video.

At night, Gaza is pitch black, with no street lights or electricity in most homes. On street corners, makeshift fires can be seen burning, with small crowds gathered for warmth.

The noise of generators can be heard from some factories and wealthier households, but most cannot afford to run diesel generators 20 hours a day.

Bakery owner Haitham Badra said he had suffered huge losses because he had to buy more fuel for generators.

"We used to buy 1,500 litres of diesel week. Now we have to buy 4,000 litres at a cost of 20,000 shekels ($5,250) a week," said Badra. "If the crisis continues much longer, all bakeries and restaurants in Gaza will collapse."

Tareq Lubbad, spokesman of the power company, said Gaza normally needed 450 MW a day, but that had increased due to high winter demand. He warned of deeper cuts to come.

"If no substantial solutions are found the crisis will escalate and hours without power will increase," he said. (Editing by Luke Baker and Angus MacSwan)